NADH:Fe(III)‐chelate reductase of maize roots is an active cytochrome b 5 reductase

Microsomal NADH:Fe(III)‐chelate reductase (NFR) of maize roots has been purified as a monomeric flavoprotein of 32 kDa with non‐covalently bound FAD. In the presence of NADH, NFR efficiently reduced the physiological iron‐chelate Fe(III)‐citrate (K cat/K m(Fe(III)‐citrate)=6.0×106 M−1 s−1) with a se...

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Bibliographic Details
Published in:FEBS letters 1997-09, Vol.414 (3), p.571-575
Main Authors: Sparla, Francesca, Bagnaresi, Paolo, Scagliarini, Sandra, Trost, Paolo
Format: Article
Language:English
Subjects:
b 5R
Cytochrome b 5 reductase
Fe(III)-citrate
ICM
intracellular membranes
Iron reduction
NADH:Fe(III)-chelate reductase
NFR
p-hydroxymercuribenzoic acid
PHMB
plasma membrane
Zea mays
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Summary:Microsomal NADH:Fe(III)‐chelate reductase (NFR) of maize roots has been purified as a monomeric flavoprotein of 32 kDa with non‐covalently bound FAD. In the presence of NADH, NFR efficiently reduced the physiological iron‐chelate Fe(III)‐citrate (K cat/K m(Fe(III)‐citrate)=6.0×106 M−1 s−1) with a sequential reaction mechanism. Purified NFR was totally inhibited by the sulfhydryl reagent PHMB at 10−9 M, and it could use cyt b 5 as alternative electron acceptor with a maximal reduction rate as high as with Fe(III)‐citrate. We conclude that in maize roots the reduction of Fe(III)‐citrate is chiefly performed by a cytochrome b 5 reductase, mostly associated with intracellular membranes and in part with the plasma membrane.
ISSN:0014-5793
1873-3468
DOI:10.1016/S0014-5793(97)01073-9